The present invention relates to high density electrical connectors, and particularly relates to a connector system for use with one or more pairs of flex circuits.
Flex circuits are well known as a way of extending multiple parallel electrical conductors. Generally, they include a flexible substrate of a dielectric material such as a polyimide resin on which are located small, closely-spaced conductor traces, useful, for example, for interconnecting circuit boards to one another, or for connecting circuit boards to flexible cables of different types. In order to provide a reliable electrical connection between flex circuits it is important to press together corresponding conductor traces of mating flex circuits with sufficient pressure to exclude gas which might corrode the material of the conductor traces in the area of contact. Interconnection of a mating pair of flex circuits has been accomplished previously by the use of resiliently compressible solid bodies, such as rubber strips located between clamping bodies, to press mating conductor traces together despite irregularities in thickness of the flex circuits in the area of interconnection, as shown, for example, by Martellotti U.S. Pat. No. 4,971,575. The performance of a solid compressible member has been found to be somewhat less than desired, however, since it does not result in equal distribution of pressure. Additionally, many elastomers will creep with time and thus lose compressive force and become ineffective. Pairs of conductor traces which are pressed together with a smaller amount of pressure in use of such previously-known devices may not achieve satisfactory electrical contact or may be subject to early deterioration of contact surfaces as a result of the ability of corrosive components of the atmosphere to reach such surfaces.
Additionally, because of the perceived need to apply adequate pressure to hold together each pair of corresponding conductor traces of a pair of flex circuits being interconnected with each other, a separate pair of clamping bodies has been considered to be necessary for each junction between a pair of flex circuits.
It has been known in the past to use flex circuits to make electrical connection to printed circuit boards to connect such circuit boards electrically into larger electronic devices, and to attach them mechanically. Fox, Jr. U.S. Pat. No. 4,968,265, and Fox, Jr. U.S. Pat. No. 5,002,496 disclose the use of a fluid-filled bladder interacting between a backing member and a flex circuit to transmit fluid pressure to connect a flex circuit to a circuit board.
An IBM Technical Disclosure Bulletin, Vol. 8, No. 4, pp. 518-519, dated September 1965, by P. E. Stuckert, discloses a transmission line connector utilizing a pair of expansible metallic bladders which may be inflated by pressurized fluid to urge mating surfaces together to provide electrical contact.
Wakabayashi et al. U.S. Pat. No. 4,538,865 discloses use of a connector to mate a single pair of printed circuit boards by using an elastic member to provide compliant pressure against one of the pair of mated circuits aligned with one another by screws passing through holes defined in the printed circuit boards.
None of the prior art known to the inventors hereof, however, has provided a connector capable of interconnecting multiple superimposed pairs of flex circuits at a single connector, between a single pair of clamping bodies.
In some applications, such as certain medical diagnostic equipment, it is necessary to provide reliable interconnection, between flexible cables having hundreds of individual electrical conductors and associated portable sensor bodies, or between such cables and circuits of stationary electronics equipment. Particularly with respect to such a movable sensor head attached to such a flexible cable, it is often desirable to minimize the size of the sensor head. Accordingly, it is desired to provide connection between the flexible cable and such a portable sensor through as small a connector as is practical.
What is desired, then, is an improved connector for interconnecting multiple pairs of multi-conductor flex circuits at a single location and with a minimum amount of space being occupied by a connector assembly or assemblies, in order to provide increased density of electrical interconnection of pairs of conductors.